Shadows Volumes & Convex areas

I’m trying to optimise my shadow volumes at the moment and obviously the biggest hit with the stencil/volume approach is it’s usage of fill rate. All I can think of so far is clipping the volumes against the geometry (Only for precalculated volumes), and segmenting my world into convex regions as then only the edges to the portals of these regions would be capable of casting shadows - which hopefully will help towards cutting down the number of edges I have to check (Useful for dynamic volumes) and go someway towards figuring out which volumes are visible in each region (Which I suppose could be precalculated also - which would involve clipping volumes to portals). I was wondering if anyone had experimented with similar ideas and if anyone knew of some good references to the actual process of carving up a triangle (soup) database into convex regions.

Also has anyone come close to combining a stencil shadow volume technique with some fiddling with destination alpha and projective texturing to produce soft shadows?

Tried to do soft shadows using shadow volume and texture projection and it seemed to nearly work with just the odd artifact here and there but it was never perfect.

Then my hard drive died and like a fool I hadn’t backed it up - whoops!!

All of your ideas sound feasible though although if you’re using shadow volumes from the lights POV the knowing which edges can cast shadows won’t help (at least I can’t think of a way it will help) as you still have to render from the lights POV.

Also, if you haven’t got it; get the book - Game Programming Gems. It’s got a very in depth section on volume shadowing with some excellent tutorial programs on the CD


Determining which edges can cast shadows (They should only be the edges of portals as the regions should be convex) saves me having to go through all edges to determine shadow volumes.

[This message has been edited by UncleBuck (edited 04-06-2001).]